Blindness and Visual Impairment due to Age-Related Cataract in sub- Saharan Africa: Systematic review of recent population-based studies
Andrew Bastawrous1, William H Dean2,3, Justin C Sherwin4,5
1 International Centre for Eye Health, Clinical Research Department
London School of Hygiene & Tropical Medicine
2 Nkhoma Eye Hospital, Malawi
3 Ophthalmology Department, Cheltenham General Hospital, UK
4 Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, UK
5 Lions Eye Institute, University of Western Australia, Australia
Please address all correspondence to:
Mr. Andrew Bastawrous BSc (Hons) MBChB HFEA MRCOphth
MRC Clinical Research Fellow in International Eye Health
International Centre for Eye Health, Clinical Research Department, Faculty of
Infectious and Tropical Diseases
London School of Hygiene & Tropical Medicine
Keppel Street, London, WC1E 7HT, UK.
Email: [email protected]. Phone: +44 207 958 8333
Submission to BJO Global Issues
Short-running title: Cataract in Africa
Keywords: Cataract, Epidemiology, visual impairment, Blindness, Sub- Saharan Africa
Word count: 2156 Abstract word count: 201 Tables: 5 References: 40 ABSTRACT
Aim
We aimed to evaluate age-related cataract as a contributor to blindness and
visual impairment (VI) in sub-Saharan Africa (SSA).
Methods
Systematic review of population-based studies published between 2000 and
October 2012. Prevalence and proportions of blindness and VI due to
cataract, cataract surgical coverage (CSC), % intraocular lens (IOL)
implantation and visual outcomes of surgery in accordance with WHO criteria
were ascertained.
Results
Data from 17 surveys (subjects mostly aged ≥50 years old) from 15 different
countries in SSA were included, comprising 96,402 people. Prevalence of
blindness (presenting visual acuity<3/60 in better eye) ranged from 0.1% in
Uganda to 9.0% in Eritrea, and the proportion of total blindness due to cataract ranged between 21 and 67%. Cataract was the principal cause of blindness and VI in 15 and 14 studies, respectively. There was a strong positive correlation between good visual outcomes and IOL use (R=0.69,
P=0.027). Considerable inter-study heterogeneity was evident in CSC and
visual outcomes following surgery, and between 40 and 100% of operations
had used IOL’s.
Conclusions
Cataract represents the principal cause of blindness and VI and should
remain a priority objective for eye care in SSA. However, the prevalence of blindness and VI due to cataract was variable and may reflect differences in the availability of cataract surgical programmes and cataract incidence. INTRODUCTION
Cataract can manifest across one’s lifespan but its prevalence and incidence
rise with increasing age. Age-related (or senile) cataract is the most common
cause of cataract in adults. The burden of cataract is expected to continue to
pose a greater challenge to health care systems worldwide in future years,
consistent with population ageing and increases in life expectancy.1 Of 39
million people estimated to be blind worldwide in 2010, 51% of cases were
attributed to cataract.2 Regional variations in the prevalence and incidence of
blindness and visual impairment (VI) due to age-related cataract exist, with a
disproportionate prevalence in low and middle-income populations. Africa is
home to 11.9% of the global population, but 15% of the world’s blind, the
majority of which is due to cataract.2
As no effective prevention strategies exist, management of cataract is
principally surgical removal of the lens with simultaneous correction of aphakia. In SSA, extra-capsular cataract extraction (ECCE) is usually now
performed, increasingly using a small-incision approach, although the use of
phacoemulsification is rising. Cataract surgery constitutes one of the most
cost-effective of all health interventions.3 Blindness and VI due to cataract is
associated with reduced quality of life4 and visual function, which can be
ameliorated following surgical management.5 Considerable social and
economic disadvantages can result from cataract, especially in poor
communities and contributes to the perpetual cycle of poverty.6 Indeed,
provision of cataract surgery may be an effective tool in poverty alleviation.7
Management of cataract is recognised as a priority of the VISION2020: The
Right for Sight global strategy that targets avoidable blindness. Knowledge of the epidemiology of cataract is crucial for eye care programmes in sub-Saharan Africa (SSA) to effectively plan public health eye care. Since the implementation of VISION2020, several population-based blindness surveys have been conducted globally to guide the implementation, development and extension of services, which include provision for cataract surgery. Moreover, newer rapid assessment methodologies have been developed and used including the rapid assessment of avoidable blindness
(RAAB), an extension of the rapid assessment of cataract surgical services
(RACSS).8 We aimed to determine the recent epidemiology of blindness and visual impairment (VI) due to cataract in SSA by investigating its prevalence and public health impact via assessment of relevant WHO targets and indicators.3
METHODS
Our literature search was conducted for the years 2000 – October 2012 using
Medline, Embase and Google Scholar. Key words used included but were not
limited to: cataract, lens opacity, visual impairment, low vision, blindness,
presenting visual acuity, prevalence, and population. All 48 SSA African countries as well as “Africa” and “sub-Saharan Africa” were used in the search terms. Studies were included if they were population-based with a sample size > 1000, reported presenting visual acuity (PVA) with its causes, had a high participation rate (>75%) and provided the standard WHO categories of visual acuity. We also searched reference lists of studies meeting inclusion criteria. Published studies, reported in English, French and Portuguese languages were included.
Where a population-based study of blindness had taken place more than once in a single country, data from the more recent survey (provided methodology was equivalent or superior) is presented, unless two separate geographical areas within the same country were sampled within five years of one another. Estimates from national surveys were used in preference to
regional estimates from the same country. Both detailed population-based
surveys and rapid assessment methods (RACSS and RAAB) were included.
Blindness was defined using WHO criteria as PVA in the better eye of
<3/60 (<20/400; <1.30 LogMAR) while VI was defined as PVA in the better
eye of <6/18-3/60 (<20/60-20/400; <0.48-1.30 LogMAR), representing the
sum of moderate and severe VI. Thus, we did not investigate mild VI. All-
cause prevalence of blindness and VI were extracted from each study, as well
as the proportion of blindness and VI due to cataract. Based on this information, the sample population prevalence of cataract blindness and cataract-related VI were computed using the denominator (number of persons examined), while the numerator was calculated using the proportion of blindness/VI due to cataract. We also extracted CSC (at PVA<3/60 and
PVA<6/18 levels for persons), visual outcomes following cataract surgery and their causes [good (PVA>6/18), borderline (6/18 to 6/60) and poor
(PVA<6/60)], and % IOL implantation. CSC was calculated as CSC=a/(a+c)
[where a=aphakic or pseudophakic, c=cataract blindness or VI]. Lastly, we collected data on barriers to cataract surgery (unoperated subjects) and satisfaction with surgery (operated subjects). RESULTS
Data from a total of 17 surveys from 15 different countries in SSA were
included, encompassing 96,402 subjects who were examined (Table 1). Most studies examined only adults aged ≥40 or ≥50 years, however two studies included all ages, 9,10 and one ≥5 years. 11 There were two studies from
Cameroon, representing one rural and one urban district.12,13 The only other
country contributing two separate published studies was Tanzania, including
RAAB surveys from Kilimanjaro and Zanzibar.14 15 Additional RAAB surveys were performed in Botswana 16, Burundi17, Malawi 18, Rwanda19, Eritrea20, and
Kenya.21 Five studies were national surveys. 16,20,9,11,22 All studies employed
cluster random sampling, with differences in the sampling used within cluster.
Blindness prevalence ranged from 0.4% in Uganda to 9.0% in
Eritrea (Table 2). Only two studies - Eritrea and Ethiopia - had blindness
prevalence estimates exceeding 5%. Cataract accounted for between 21% of
blindness in Cameroon and the highest proportion, 67%, was in Zanzibar,
Tanzania. Cataract was the principal cause of blindness in 15 of 17 studies.
The prevalence of VI (sum of moderate and severe VI) ranged from
1.6% in Gambia and Uganda to 17.1% in Ghana (Table 3). Cataract was the
major cause of VI in 14 of 17 studies. The prevalence of VI due to cataract
ranged from 18 to 87%.
CSC data were variable, and for blind persons ranged from 15% in
Burundi to 80% in Limbe, Cameroon. This included aphakia and
pseudophakia; and for patients who had received cataract surgery, between
62% and 100% had an IOL (Table 4). In terms of PVA, the proportion of good outcomes ranged from 23% to 70%. Poor outcomes (VA<6/60) accounted for more than 20% in all studies and ranged from 23% to 64%.
There was a strong positive correlation between good visual outcomes and IOL use (R=0.69, P=0.027). There was an inverse correlation between
IOL use and poor visual outcome (R=-0.31, P=0.384). [There was an inverse relationship between the proportion of blindness due to cataract and CSC
(persons, blindness): R=-0.50, P=0.137. There was an inverse relationship between CSC (blind) and good visual outcome: R=-0.34, P=0.37].
Causes of a poor visual outcome, barriers to cataract surgery and satisfaction rates with surgery were identified (Table 5). Insertion of an IOL is consistently associated with having a good visual outcome. Lack of awareness and inability to pay were frequently cited as major barriers to cataract surgery. The majority of individuals surveyed reported being satisfied with their surgery.
DISCUSSION
We have provided an up-to-date review on blindness and VI due to cataract in
SSA obtained from 17 studies of nearly 100,000 individuals. Wide differences in estimates of blindness and VI prevalence due to cataract were evident in this study, but cataract remains the principal cause of blindness in SSA.
Although cataract prevalence is high in some Asian and South American populations it is on average lower than Africa and much lower in areas of higher HDI.23
Unsurprisingly, the population with the lowest blindness prevalence in
this study, Uganda, has had a strong recent history of successful eye care
programme delivery. The differences between countries are striking: a 74-fold
difference in cataract blindness prevalence between Uganda and Mali who
have similar GDP (Per-capita) of US$487 and US$669 respectively (World
Bank 2011). Successful blindness prevention programme delivery and
available cataract surgical services and human resources especially in rural
areas, shorter distances and easier transport for patients, affordable fee
structures or free services, and cultural barriers to service access may
account for these huge differences. Further studies are required to quantify
the resources required to make such differences, and to examine how this
has been achieved.
It has been suggested that a cataract surgical rate (CSR) of ≥ 2,000
operations/million population/year should be achieved annually to eliminate unnecessary blindness due to cataract in Africa.24 This benchmark is in stark
contrast to the current situation in many parts of Africa, with over 80% of
WHO member states in Africa having a CSR<1000.3 A substantial increase in CSR is needed to reduce blindness and VI due to cataract in SSA. Worse HDI ranks are associated with a higher prevalence of cataract blindness, and in
SSA a much higher proportion of individuals undergoing surgery for cataract have pre-operative blindness or SVI compared to higher-income populations.25 The challenge remains reaching blind and visually impaired people by providing accessible, affordable, and sustainable cataract surgical services.
Importantly, any increase in cataract surgical output is usually accompanied by an increase in outcome. The proportion of good outcomes ranged from 23% to 70%, all of which fail to reach the WHO target that ≥ 85% of eyes should achieve PVA<6/18 post-operatively.
These proportion of good visual outcomes in most studies were markedy lower than from recent hospital-based studies on this continent.26 27 Prospective monitoring of outcomes can improve quality,28 with a dynamic and learning process for the surgeon of focusing on reducing surgical complications, greater emphasis on appropriate selection, need for spectacle correction, and sequelae of surgery. In many settings non-physician cataract surgeons provide the majority of cataract surgery. There remains controversy as to whether this cadre of surgeon is ideal to meeting the cataract surgical needs in
SSA. Greater regulation and long-term training of physician-surgeons may provide a better long-term solution.
Population-based data on visual outcomes is highly valuable as clinic/hospital based outcome estimates are not often representative of the visual status in the community. However, as modern techniques using ECCE with IOL implantation are now ubiquitous in almost all
areas of SSA, population-based outcomes are likely to be worse as they
may capture outcomes for surgeries performed up to many years prior
(e.g. ICCE). Uncorrected aphakia remains an important contributor to
blindness and VI in many areas of SSA.29 More recently performed
cataract surgery is associated with more frequent use of lOLs2130, which
in turn is positively correlated with a good visual outcome. In some
areas, cataract removal by couching leading to aphakia is associated
with extremely poor visual outcomes, even with aphakic correction.31
Poor visual outcomes ranged from 23% to 64%, with the causes
of poor outcomes being variable, and representing differences in
expertise, resources and monitoring/surveillance. Understanding the
causes of such poor outcomes is vital. Visual outcomes can be ameliorated with improved case selection and avoidance of surgery in patients who won’t benefit; improving the quality of surgery and avoiding surgical complications; improving the operative (IOL) and/or post- operative correction of refractive error and; reducing late post-operative complications.32 Further cataract surgery outcomes data is needed from
studies in SSA, and globally, to assess not only the importance and
complexity of good outcomes and to revisit the parameters set by the
WHO, but most importantly to understand and disseminate knowledge about how to improve outcomes.
It is intuitive that in order to reduce the blindness and VI due to cataract
the CSR needs to exceed the cataract incidence rate. Lewallen et al. have modeled the incidence of vision-reducing cataract in Africa using data from
RAAB surveys.33 Such derived estimates may assist further with the planning of services in this resource-poor region where incidence estimates are scarce, and have indicated disparities in cataract incidence in this continent. WHO recommends the establishment of ≥ one cataract unit per district of a million population in order to deal with cataract blindness and VI.3 CSR’s also reflect variations in genetic, environmental, or cultural factors and will vary with population structure, which is not uniform across Africa.33
Two indicators can measure the impact of initiatives to target cataract.
Firstly, performing serial cross-sectional population-based surveys to demonstrate evidence of a reduction in prevalence of cataract (and blindness and VI due to cataract) over time.34 35 Another indicator is to measure the
CSC which represents a ratio of the met and unmet need for cataract surgery, and is a measurement of the capability of a health care system to provide cataract surgical services to the population.36 In these studies, the CSC for persons for blinding cataract ranged from 22 to 70%, and was usually higher in men reflecting a probably gender inequity in access to cataract surgical services.37 CSR is positively correlated with CSC,25 but CSC does not take into account the quality of surgery provided.
There are several limitations to this review. Inter-study differences exist in relation to the size, age/gender composition, response rates and degree of urbanization as well as degree of government and non-government organization involvement in the surveyed areas. Such differences may account for some of the heterogeneity between individual results. RAAB surveys have several disadvantages including their lack of detailed cataract phenotype information. Nonetheless, the validity of the RAAB compared to a more detailed survey is high.38
In conclusion, cataract is by far the most common cause of blindness and VI in SSA. Efforts to reduce the burden of blindness and VI due to cataract should incorporate high-volume, high-quality, affordable cataract surgery that greatly improves the CSR and CSC in such populations. This can be achieved by the implementation of well-run, cost-effective, and sustainable cataract units at the district level. Wide variation in the prevalence of cataract blindness has been shown in this review, and although this may be due to disparities in eye care programme delivery, it may also reflect inter-population differences in cataract incidence. The fundamental problems highlighted by this review are that currently too few cataract surgeries are being performed and there are too many poor outcomes. An open and urgent appraisal of positive successes throughout SSA should be performed and shared.
Funding statement:
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
Competing Interests Statement:
No, there are no competing interests
Contributorship Statement:
AB extracted the data and designed the study and contributed to writing the manuscript. JS and WD analysed the data and wrote the manuscript. All authors were responsible for revising and approving subsequent drafts of the article prior to submission. AB is the guarantor of the article.
REFERENCES
1. Bongaarts J. Human population growth and the demographic transition.
Philos Trans R Soc Lond B Biol Sci 2009;364(1532):2985-90.
2. Pascolini D, Mariotti SP. Global estimates of visual impairment: 2010. Br J
Ophthalmol 2012;96(5):614-8.
3. World Health Organization. Global Initiative for the Elimination of Avoidable
Blindness : action plan 2006-2011. Geneva, 2007.
4. Nirmalan PK, Tielsch JM, Katz J, et al. Relationship between vision
impairment and eye disease to vision-specific quality of life and
function in rural India: the Aravind Comprehensive Eye Survey. Invest
Ophthalmol Vis Sci 2005;46(7):2308-12.
5. Desai P, Reidy A, Minassian DC, et al. Gains from cataract surgery: visual
function and quality of life. Br J Ophthalmol 1996;80(10):868-73.
6. Kuper H, Polack S, Eusebio C, et al. A case-control study to assess the
relationship between poverty and visual impairment from cataract in
Kenya, the Philippines, and Bangladesh. PLoS Med 2008;5(12):e244.
7. Kuper H, Polack S, Mathenge W, et al. Does cataract surgery alleviate
poverty? Evidence from a multi-centre intervention study conducted in
Kenya, the Philippines and Bangladesh. PLoS One 2010;5(11):e15431.
8. Dineen B, Foster A, Faal H. A proposed rapid methodology to assess the
prevalence and causes of blindness and visual impairment. Ophthalmic
Epidemiol 2006;13(1):31-4.
9. Berhane Y, Worku A, Bejiga A, et al. Prevalence and causes of blindness
and Low Vision in Ethiopia. Ethiopian Journal of Health Development
2007;21(3):204-210. 10. Moser CL, Martin-Baranera M, Vega F, et al. Survey of blindness and
visual impairment in Bioko, Equatorial Guinea. The British journal of
ophthalmology 2002;86(3):257-60.
11. Faal H, Minassian DC, Dolin PJ, et al. Evaluation of a national eye care
programme: re-survey after 10 years. The British journal of
ophthalmology 2000;84(9):948-51.
12. Oye JE, Kuper H. Prevalence and causes of blindness and visual
impairment in Limbe urban area, South West Province, Cameroon. The
British journal of ophthalmology 2007;91(11):1435-9.
13. Oye JE, Kuper H, Dineen B, et al. Prevalence and causes of blindness
and visual impairment in Muyuka: a rural health district in South West
Province, Cameroon. The British journal of ophthalmology
2006;90(5):538-42.
14. Habiyakire C, Kabona G, Courtright P, et al. Rapid assessment of
avoidable blindness and cataract surgical services in kilimanjaro
region, Tanzania. Ophthalmic epidemiology 2010;17(2):90-4.
15. Kikira S. RAAB survey of Pemba and Unguja islands, Zanzibar.
Community eye health / International Centre for Eye Health
2007;20(64):71.
16. Nkomazana O. Disparity in access to cataract surgical services leads to
higher prevalence of blindness in women as compared with men:
results of a national survey of visual impairment. Health Care Women
Int 2009;30(3):228-9. 17. Kandeke L, Mathenge W, Giramahoro C, et al. Rapid Assessment of
Avoidable Blindness in Two Northern Provinces of Burundi without Eye
Services. Ophthalmic epidemiology 2012;19(4):211-5.
18. Kalua K, Lindfield R, Mtupanyama M, et al. Findings from a rapid
assessment of avoidable blindness (RAAB) in Southern Malawi. PLoS
One 2011;6(4):e19226.
19. Mathenge W, Nkurikiye J, Limburg H, et al. Rapid assessment of
avoidable blindness in Western Rwanda: blindness in a postconflict
setting. PLoS medicine 2007;4(7):e217.
20. Muller A, Zerom M, Limburg H, et al. Results of a rapid assessment of
avoidable blindness (RAAB) in Eritrea. Ophthalmic Epidemiol
2011;18(3):103-8.
21. Mathenge W, Kuper H, Limburg H, et al. Rapid assessment of avoidable
blindness in Nakuru district, Kenya. Ophthalmology 2007;114(3):599-
605.
22. Rabiu MM. Prevalence of blindness and low vision in north central,
Nigeria. West African journal of medicine 2008;27(4):238-44.
23. Shah SP, Gilbert CE, Razavi H, et al. Preoperative visual acuity among
cataract surgery patients and countries' state of development: a global
study. Bull World Health Organ 2011;89(10):749-56.
24. Vision 2020: the cataract challenge. Community Eye Health
2000;13(34):17-9.
25. Murthy G, John N, Shamanna BR, et al. Elimination of avoidable
blindness due to cataract: where do we prioritize and how should we
monitor this decade? Indian J Ophthalmol 2012;60(5):438-45. 26. Sherwin JC, Dean WH, Schaefers I, et al. Outcomes of manual small-
incision cataract surgery using standard 22 dioptre intraocular lenses at
Nkhoma Eye Hospital, Malawi. Int Ophthalmol 2012;32(4):341-7.
27. Trivedy J. Outcomes of high volume cataract surgeries at a Lions Sight
First Eye Hospital in Kenya. Nepal J Ophthalmol 2011;3(1):31-8.
28. Yorston D, Gichuhi S, Wood M, et al. Does prospective monitoring
improve cataract surgery outcomes in Africa? Br J Ophthalmol
2002;86(5):543-7.
29. Sherwin JC, Lewallen S, Courtright P. Blindness and visual impairment
due to uncorrected refractive error in sub-Saharan Africa: review of
recent population-based studies. Br J Ophthalmol 2012;96(7):927-30.
30. Imam AU, Gilbert CE, Sivasubramaniam S, et al. Outcome of cataract
surgery in Nigeria: visual acuity, autorefraction, and optimal intraocular
lens powers--results from the Nigeria national survey. Ophthalmology
2011;118(4):719-24.
31. Gilbert CE, Murthy GV, Sivasubramaniam S, et al. Couching in Nigeria:
prevalence, risk factors and visual acuity outcomes. Ophthalmic
Epidemiol 2010;17(5):269-75.
32. Limburg H. Monitoring Cataract Surgical Outcome (MCSO) for Windows.
(Version 2.4 – November 2009). : International Centre for Eye Health,
2010.
33. Lewallen S, Williams TD, Dray A, et al. Estimating incidence of vision-
reducing cataract in Africa: a new model with implications for program
targets. Arch Ophthalmol 2010;128(12):1584-9. 34. Dean WH, Patel D, Sherwin JC, et al. Follow-up survey of cataract
surgical coverage and barriers to cataract surgery at nkhoma, Malawi.
Ophthalmic Epidemiol 2011;18(4):171-8.
35. Faal H, Minassian DC, Dolin PJ, et al. Evaluation of a national eye care
programme: re-survey after 10 years. Br J Ophthalmol 2000;84(9):948-
51.
36. Limburg H, Foster A. CATARACT SURGICAL COVERAGE: An indicator
to measure the impact of cataract intervention programmes.
Community Eye Health 1998;11(25):3-6.
37. Lewallen S, Mousa A, Bassett K, et al. Cataract surgical coverage
remains lower in women. Br J Ophthalmol 2009;93(3):295-8.
38. Mathenge W, Bastawrous A, Foster A, et al. The nakuru posterior
segment eye disease study: methods and prevalence of blindness and
visual impairment in nakuru, kenya. Ophthalmology
2012;119(10):2033-9.
Table 1. Population-based studies from sub-Saharan Africa with data on blindness and age-related cataract
Year Sampling Sample size Response Age Country Level Sampling within cluster Ref Published Method (number examined) Rate (%) (years)
Botswana National 2009 CRS Compact segment sampling 2127 79.9 ≥50 16 Burundi Provincial 2012 CRS Compact segment sampling 3684 97 ≥50 41 12 Cameroon Limbe 2007 CRS Compact segment sampling 2215 92.3 ≥40 13 Cameroon Muyuku 2006 CRS Random Walk 1787 89.3 ≥40
CRS 20 Eritrea National 2011 Compact segment sampling 3163 95.9 ≥50 9 Ethiopia National 2007 CRS Random Walk 25650 85.4 All 11 Gambia National 2000 CRS Compact segment sampling 13046 92 ≥5 42 Ghana City 2012 CRS House to house census 5603 82.3 ≥40 10 Guinea District, Bioko 2002 CRS Household cluster sampling 3218 NS All 21 Kenya District, Nakuru 2007 CRS Compact segment sampling 3503 92.6 ≥50 18 Malawi District 2011 CRS Compact segment sampling 3430 95.7 ≥50 Mali Sub-national 2008 CRS Compact segment sampling 2438 NS ≥50 22 Nigeria National 2009 CRS Random Walk 13599 89.9 ≥40 19 Rwanda Western province 2007 CRS Compact segment sampling 2206 98 ≥50 43 South Sudan District 2006 CRS Random Walk 2499 84.6 ≥5 Tanzania CRS 14 (Kilimanjaro) Regional 2010 Random Walk 3436 95.5 ≥50 Tanzania CRS 15 (Zanzibar) Island 2007 Compact segment sampling 3160 98.8 ≥50 15 neighbouring 44 Uganda villages 2002 CRS NS 4076 98.9 ≥13 CRS: Cluster Random Sampling; NS- not stated
Table 2. Prevalence and leading causes of blindness (PVA < 3/60 in worse eye) in sub-Saharan Africa
Country Bilateral blindness Main cause of Proportion of 2nd Main cause of Proportion of Prevalence of Ref prevalence (95% CI) blindness blindness(%) blindness blindness (%) cataract blindness Botswana 3.69 (2.4-5.0) Cataract 47 NS NS 1.7 16 Burundi 1.1 (0.8-1.4) Cataract 55 PSED 37 0.6 41 12 Cameroon (Limbe) 1.1 (0.7-1.5) PSED 29 Cataract 21 0.2 13 Cameroon (Muyuka) 1.6 (0.8-2.4) Cataract 62 PSED & Onchocerciasis 14 1.0 Eritrea 9.0 (8.0-10.0) Cataract 55 Glaucoma 15 5.0 20
9 Ethiopia 7.9 (6.9-8.9) Cataract 50 Trachoma 20 4.0 11 Gambia* 0.42 Cataract 45 Other corneal 16 0.2 42 Ghana# 1.2 Cataract 44 Glaucoma 22 0.5 10 Guinea 3.2 (2.6-3.9) Cataract 61 Macular affection 25 2.0 21 Kenya 2.0 (1.5-2.4) Cataract 42 PSED 30 0.8 18 Malawi 3.3 (2.5-4.1) Cataract 48 Glaucoma 16 1.6 Mali 11.07 (9.55-12.6) Cataract 61 Surgical Complications 10 6.8 22 Nigeria 4.2 (3.8-4.6) Cataract 43 Glaucoma 17 1.8 19 Rwanda 1.8 (1.2-2.4) Cataract 65 PSED 20 1.2 43 South Sudan 4.1 (3.4-4.8) Cataract 41 Trachoma 35 1.7 14 Tanzania 2.4 (1.9-2.9) Cataract 51 PSED 36 1.2 (Kilimanjaro) 15 Tanzania (Zanzibar) 3.7 Cataract 67 PSED 25 2.5 44 Uganda 0.4 (0.3-0.7) Glaucoma 39 Cataract 23 0.1 PSED: Posterior Segment Eye Disease; CI: Confidence Interval; NS- not stated * Estimates for ≥50 years # This study excludes refractive error from table of blindness/VI aetiology.
Table 3. Leading causes of Visual Impairment (VI) in sub-Saharan Africa
Country Main cause of VI Proportion of VI (%) 2nd Main cause of VI Proportion of VI (%) Ref
Botswana Cataract 59 NS NS 16 Burundi Refractive Error 67 Cataract 18 41 12 Cameroon (Limbe) Cataract 48 Refractive Error 22 13 Cameroon (Muyuka) Cataract 40 PSED 28 Eritrea Cataract 55 Refractive Error 31 20
9 Ethiopia Cataract 34 Refractive Error 26 11 Gambia Cataract 61 (≥ 50 years) Uncorrected aphakia 12 (≥50 years) 42 Ghana* Cataract 53* Glaucoma 14* 10 Guinea Cataract 87 Macular affection 29 21 Kenya Cataract 36 Refractive Error 32 18 Malawi Cataract 46 Refractive Error 41 Mali Cataract 61 Refractive Error 22 22 Nigeria Refractive Error 57 Cataract 26 19 Rwanda Cataract 55 Refractive Error 30 43 South Sudan Trachoma 58 Cataract 29 14 Tanzania (Kilimanjaro) Cataract 55 Refractive Error 33 15 Tanzania (Zanzibar) Cataract 47 Refractive Error 39 44 Uganda Cataract 57 Refractive Error 19 PSED: Posterior Segment Eye Disease; VI- Visual Impairment; NS- not stated VI 6/18 to 3/60 * This study excludes refractive error from table of blindness/VI aetiology.
Table 4. Cataract Surgical Coverage, Visual outcomes following cataract surgery, and %IOL use in sub-Saharan Africa
Country CSC (VA<6/18) persons CSC (blind persons [PVA<3/60]) Visual outcome (PVA) IOL Total Males Females Total Male Female Good Poor (% of all persons persons (PVA>6/18) (PVA<6/60) operated eyes) Botswana 53 62 48 62 73 55 NS NS NS Burundi 12 9 13 22 17 24 70 30 100 Cameroon (Limbe) NS NS NS 80 NS NS 23 58 69 Cameroon (Muyuka) NS NS NS 55 NS NS 25 64 68 Eritrea 48 50 46 68 71 65 41 39 75 Kenya 51 51 51 78 78 78 50 31 58 Malawi 16 25 10 45 62 30 41 32 68 Mali 34 39 30 59 70 51 28 58 33 Nigeria NS NS NS NS NS NS 30 41 40 Rwanda 21 24 19 47 64 36 24 41 62 Tanzania 42 48 37 70 73 67 59 23 87 (Kilimanjaro) Tanzania (Zanzibar) 20 25 17 60 77 49 32 38 68
CSC- cataract surgical coverage; NS- not stated; PVA- presenting visual acuity; IOL- intraocular lens No data was available from Ethiopia, Ghana, Guinea, South Sudan and Uganda
Table 5: Causes of poor outcome and barriers to cataract surgery in studies with available data in sub-Saharan Africa
Country Causes of poor outcome Associations with poor outcome Barriers to Surgery Satisfaction with surgery (post-operative subjects) Selection/Co- Surgical Uncorrected morbdity complications refractive error, aphakia, late sequelae Cameroon (Limbe) NS Inability to pay (40%), lack of NS Aphakia (compared to IOL use). awareness (17%), a feeling they could cope with the cataract (10%) and that they were waiting for Older age. cataract to mature (8%). Cameroon (Muyuka) NS Lack of awareness of cataract NS Aphakia (compared to IOL use). (33.3%), inability to pay (30.1%), and a feeling they could cope with the cataract (9.6%). Older age. Eritrea 27% 24% 48% 30% reported “Cannot afford”, NS Having surgery performed at a followed by “Waiting for maturity” voluntary or charitable hospital (18%), “No company” (17%), compared to a government hospital “Contra-indication” (12%) and “Old age, no need” (10%). Kenya 36% 30% 34% Not specified for poor outcome. 64% were very satisfied, “Not aware of surgery” (34.1%), 19% were somewhat However, good outcome was more “cannot afford the operation” satisfied, 5% were likely if the surgery was with an IOL, (24.4%), and “no one to take me” indifferent, and 12% were performed in last 5 years or (12.2%). somewhat or very undertaken in a volunteer/charity dissatisfied. hospital or private hospital rather than government hospital or eye camp Malawi 40% 47% 13% 84.8% of all persons who NS Old age (‘no need felt’) was had surgery were either reported to be the commonest very satisfied or partially barrier (23.5%) followed by ‘no satisfied. Only 3% of one to accompany’ (22.1%), ‘no persons were very services nearby’ (13.2) and unsatisfied with the results ‘unaware that treatment was of surgery. available’ (11.8%). Nigeria NS 50% Cost of surgery (over a third), NS NB: Barriers refers to 19% In multivariate analysis of data on other personal factors (a quarter), Abubakar et al. first-operated eyes, the only variable and another quarter cited barriers Coverage of Hospital- associated with poor outcome (<6/60 such as being too old, not knowing based Cataract where to go and fear of surgery. This refers to: Imam et al. Outcome of Cataract at presentation) was non-IOL surgery. Surgery and Barriers Provider-related factors, such as Surgery in Nigeria: to the Uptake of being told to attend later, were Surgery among reported by 9.8%. Cataract Visual Acuity, Autorefraction, and Optimal There were significant rural/urban Blind Persons in Intraocular Lens Powers—Results from the differences in cost as a barrier. Nigeria: Nigeria National Survey
Rwanda 25% 50% 25% Lack of awareness of the 41% were very satisfied, NS availability of treatment (52%), 28% were partially followed by a perceived lack of satisfied, indifferent (7%), services (16%), inability to afford partially dissatisfied (17%), the surgery (16%), and lack of a or very dissatisfied (7%). companion (8%). Tanzania 31% 38% 25% Eyes with an IOL had significantly NS NS (Kilimanjaro) better vision than eyes without Tanzania (Zanzibar) Unaware of treatment (30%), 56% very satisfied, 25.9% The major cause of poor outcome for operations NS waiting for cataract to mature partially satisfied, 7.9% >3yrs ago was selection and presently it is due to (20%) and cost (10%). very dissatisfied sequale. Surgery was a major cause for poor outcome for both time periods.
Key- NS- not stated; URE- uncorrected refractive error